Cobalt (ii) and manganese (ii) chelates as photographic emulsion antifoggants

ABSTRACT

PHOTOGRAPHIC LIGHT-SENSITIVE SILVER HALIDE EMULSIONS ARE DESCRIBED WHICH INCLUDE A COBALT (II) OR A MANGANESE (II) CHELATE OF A (POLY) AMINO-(POLY)CARBOXYLIC ACID IN ACID FORM OR IN THE FORM OF A WATER-SOLUBLE SALT. THESE MATERIALS EXERT AN EXCELLENT STABILIZING AND FOG-INHIBITING ACTION UPON THE PHOTOGRAPHIC LIGHT-SENSITIVE MATERIALS.

United States Patent 01 fice ABSTRACT OF THE DISCLOSURE Photographic light-sensitive silver halide emulsions are described which include a cobalt (II) or a manganese (II) chelate of a (poly) amino-(poly)carboxylic acid in acid form or in the form of a water-soluble 'salt. These materials exert an excellent stabilizing and fog-inhibiting action upon the photographic light-sensitive materials.

This invention relates to fog-inhibiting agents and stabilizers for photographic light-sensitive silver halide emulsions and to photographic emulsions containing them.

Light-sensitive silver halide emulsions are in general characterised by their sensitivity, gradation and fog.

As is well-known, sensitivity, gradation and fog are determined by the way in which the silverhalide, emulsiori is prepared and bythe use of special chemical ingredients effecting a desired improvement or result. Ad-

denda to the emulsion, which are of particular import ance for the stability of the light-sensitive characteristics of a silver halide emulsion are the so-called stabilizers.

Stabilizers or antifoggants protect the light-sensitive silver halide emulsions against spontaneous formation and growth of fog known as chemical fog during prolonged storage or storage at high temperatures and humidities or during development to maximum contrast and speed, or both. Indeed, the fog increases with the degree and temperature of development, and, constant development circumstances, with. the time the lightsensitive emulsion is stored and with the temperature and the relative humidity of the atmosphere wherein the emulsion is stored. It is evident that a light-sensitive emulsion should be obtained which is as stable as possible at high temperature andhigh relative humidity for instance in viewofits use inptropical countries. 1 It is known to protect light-sensitive silver halide emulsions against the growth of chemical fog during storage- It is also known to use heterocyclic thioxo and mercapto compounds as stabilizers 'for'photographic silver halide emulsions but thesecompounds generally show the disadvantage of impairing the sensitivity and gradation.

From United States Pat. 2,839,405 it is known that certain water-soluble inorganic acid salts, more particularly inorganic acid salts of cadmium, cobalt, manganese and zinc, are effective for inhibiting fog and stabilizing silver halide emulsions during incubation.

It has now been found that when incorporating in a light-sensitive material comprising a silver'halide emulsion layer cobalt (II) and manganese (II) chelates of (poly)amino-(poly)-carboxylic acids, in acid form or in the form of a water-soluble salt, these compounds exert a stabilizing and fog-inhibiting action upon said photographic light-sensitive material exceeding that of the simple inorganic acid salts of cobalt and manganese referred to above without causing an appreciable desensitization of said material.

Moreover, it has been found that these cobalt (II) and manganese (II) chelates are very suitable for use in combination with stabilizers of 'the triazolopyrimidine type, particularly in extreme storage and development.

circumstances in order to reduce the fogging tendency of the light-sensitive emulsion.

The cobalt (II) and manganese (II) chelates of (poly)- amino-(poly)carboxylic acids can be prepared in a very simple way, namely by allowing to react a water-soluble cobalt (II) or manganese (II) salt (chloride, acetate,

-nitrate, sulfate, etc.) with a (poly) amino-(poly)carboxylic acid sequestering compound or water-soluble salt there- Examples of suitable (poly)amino-(poly)carboxylic acid sequestering compounds for reaction with a cobalt (II) or manganese (II) salt to form the corresponding cobalt (II) and manganese (II) chelates as well as details about the preparation of said sequestering compounds can 'be found in Ind. Chim. Belg. Tome XXI (1956) pp. 338- 346 and in Ind. Chim. Belg. Tome XXIII (1958) pp. 1105-1115.

Particularly suitable (poly)amino-(poly)carboxylic acids for formin in acid or salt form with a cobalt (II) or manganese (II) salt the corresponding cobalt (II) or manganese (II) chelates can be represented by the following non-limitative general formula:

Rr-N L N wherein hydrogen, lower alkyl including substituted lower alkyl, aral-kyl including substituted-aralkyl or aryl including substituted aryl; examples of substituted alkyl groups for R and for R are alkyl substituted with hydroxyl, halogen, alkoxy, carbamoyl, amino, substituted amino e.g. dihydroxyalkylamino, epoxy, carboxyl, sulfo,

phosphono, mercapto, alkylamercapto, alkoxyc'arbonyl, a nitrogen-containing heterocyclic ring e.g. pyriclyl and examples of substituted aryl groups and aralkyl groups for R and/ or R are: aryl and aralkyl substituted by hydroxyl, halogen, alkyl, alkoxy, nitro, carboxyl and sulfo.

The following is a non-limitative list of examples of (poly)amino(poly)carboxylic acids corresponding to the above general formula:

ethylenediamine,N,N,N,N-tetraacetic acid Patented Jan. 19, 1971 ,As compared with the known cobalt and manganese compounds used as stabilizers the cobalt (II) "and manganese' (II) chelates according to the present invention when used in the appropriate concentration have a markedly better fog-inhibiting action. I

The antifoggants according to the present invention are particularly suitable for use in conjunction with compounds which sensitize the emulsion by development acceleration for example alkylene oxide polymers. These The stabilizers according to the invention can also be used in conjunction with other known stabilizers for instance with heterocy'clic nitrogen containing thioxo' compounds such as benzothiazoline 2 thione and lphenyl-Z-tetrazoline-5-thione, with mercury compounds such as those described in Belgian patent specifications 524,121 and 677,337 and in the published Dutch patent application 6715932 and, as said above, preferably with compounds of the hydroxytriazolopyrimidine type (azaindolizines). r I

The stabilizers according to the present invention may be incorporated into any type of light-sensitive material comprising a silver halide emulsion layer, e.g. a spectrally sensitizedor non-sensitized silver halide emulsion layer, a silver halide emulsion layer of use in diffusion transfer processes for the production of silver images, an X-ray emulsion layer, and an emulsion layer sensitive to infrared radiation. They may be incorporated into high-speed negative materials as well as into rather low speed positivematerials. Various silver salts may be used as light-sensitive salt e.g. silver bromide, silver iodide, silver chloride, or mixed silver halides e.g. silver-chloro-bromide'or silver bromo-iodine. a I

The silver halides are dispersed in the common hydro philic colloids such as gelatin, casein, zein, polyvinyl alcohol, carboxymethylcellulose, alginic acid, etc., gelatin"- being however favoured. The stabilizing agents are generally the silver halide emulsion layer of the light-sensitive material; they may be added to the emulsion during any step of emulsion preparation; however, they are preferably added to the photographic emulsion after chemical ripening and just before coating of the emulsion. The' addenda according to the present invention are incorporated into the photographic emulsions according to the methods well known in emulsion preparation, e.g. in the form of a solution in any convenient solvent not injurious to the emulsion such as water or lower alcohols.

Instead of incorporating the compounds of the invention into the emulsion layer they can alsobe incorporated into another layer of the photographic material, e.g. a gelatin antistress layer or intermediate layer, which is in water-premeable relationship with the said emulsion layer.

employed in the light-sensitivesilver halide material depends on the particular type of emulsion and the desired effect and canvary within very wide limits. ,The optimum amount of cobalt (II) and manganese (II) chelate to be .added can be determined'for each particular type of emulsion in a very simple way by application of the usual tests. Usually said compounds are employed in a ratio of about 0.1 g. to about g. per mole of silver incorporated into The amount of cobalt (II) and manganese (II) chelate halide, preferably from 0.5 to 10 g. per mole of silver halide, when incorporated into the emulsion layer itself,

and in an amount of about 10 mg to 1 g. per sq. m. when incorporated into a layer in water-permeable relationship with the emulsion layer.

The light-sensitive emulsions may be chemically as well as optically sensitized. They may be chemically sensitized by effecting the ripening in the presence of small amounts of sulfur containing compounds such as allylthiocyanate, allyl thiourea, sodium thiosulfate, etc. The;

emulsions may also be sensitized by means of reductors for instance tin compounds as described in our French patent specification 1,146,955 and in our Belgian patent specification 568,687, imino-amino methane sulfinic acid compounds as described in our United Kingdom patent specification 789,823 and small amounts of noble metal compounds such as of gold, platinum, palladium, iridium, ruthenium and rhodium.

Other addenda such as hardening agents, wetting agents, plasticizers, color couplers, developing agents and optical sensitizers can be incorporated into the emulsion in the usual way.

The following examples illustrate the present invention.

EXAMPLE 1 A gelatino silver bromoiodide emulsion (2 mole percent of iodide) comprising 400 mg. per mole of silver halide of 5-methyl-7-hydroxy s-triazolo [1,5-a] pyrimidine as stabilizer, and 1 g. per litre of emulsion of saponin as coating aid, was prepared in the conventional manner and then divided into 2 aliquot portions.

To emulsion portion B were added 5.5 g. per mole of silver halide of the cobalt (II) chelate of compound 1 disodium salt, whereas to emulsion portion A no cobalt (II) chelate was added.

The two emulsions were coated on both sides of a subbed cellulose triacetate support in such a way that an amount of silver halide equivalent to 10 g. of sq. m.

of silver nitrate was present. The emulsion layers were the-n overcoated with a gelatin antistress layer.

Strips of the two materials thus obtained were stored for 36 hours in an atmosphere of 57 C. and 35% relative humidity.

The stored material strips as Well as strips of the freshly prepared materials were exposed and developed for 8 minutes at 20 C. in a developing bath with the following composition:

Water-800 ccs. p Monomethylaminophenol sulphate-4 g. Sodium sulfite (cryst.)l30 g.

Hydroquinone-IO g.

Sodium carbonate (cryst.)- g. Potassium bromide-5 g. Water to make, 1000 ccs.

After the treatment in a stop bath, rinsing and fixing of the material strips the following sensitometric results were attained.

tions.

Each of the three emulsion portions was coated on both sides of 21 subbed cellulose triacetate support, in such a way that on both sides an amount of silver halide equivalent to 8 g. of silver nitrate was present per sq. m., and

dried. The emulsion layers of the three materials A,-B and C-Wer'e then overcoated with a gelatin antistress layer,- the antistress layers of materials B and C containing 0.07 and 0.28 g. per sq. m. respectively of the cobalt (II), chelate of compound 1 disodium'salt.

Ships of the three materials were conditioned in a moist atmosphere of about 75% relative humidity and then packed in aluminum-laminated paper and finally stored for 1 week at 59 C.'Other strips were stored for 36 hours in an atmosphere of 57 C. and 34% relative humidity.

The stored material strips as well as strips of the freshly prepared materials were further treated as described in Example 1.

The following sensitometric results were attained.

" The, following sensitometric results were obtainedwith freshly prepared materials and materials storedffor 1.36 hours in an' atmosphere' of 57 C. and 34% relative, humidity. i

' V Stored for 36 hours at Freshly prepared 57 0.134% RH Relative j Relative speed, Gradaspeed, percent Fog tion percent 100 0. (is as 123 89 0. 04 3. 0 100 80 0. 3. O 85 102 0. 24' 2. 7 135 89. 0. 04 3. 1 .100

Stored for 36 hrs. at 57 Stored for 1 week at. 59

C./7 7 RH Freshly prepared 0.134% RE 0 Rel. Rel. I Re-l. Gradaspeed, Gradaspeed, Gradaspeed, Material Fog tion percent Fog tion percent. Fog tion percent A 0. 09 v 2.43 100 0.12 2.18 100 0.24, 60 V 104 EXAMPLE 3 From these results it appears that the addition ofthe.

A gelatino silver bromoiodide emulsion (2 mole percent of iodide) was prepared and divided into five aliquot portions.

Each of the five emulsion portions was coated on a subbed cellulose triacetate support, in such a way that on both sides an amount of silver halide equivalent to 8 g. per sq. m. of silver nitrate was present, and dried. The emulsion layers of the five materials A, B, C, D and E were then overcoated with a gelatin antistress layer pro rata of 1 g. of gelatin per sq. m. The gelatin antistress layers of material B comprised, on each side, 250 mg. per sq. m. of the cobalt (II) chelate of compound 1 disodium salt, whereas the gelatin antistress layers of materials C, D and E comprised equivalent amounts per sq. m. of cobalt (II) sulfate, cobalt (II) acetate and cobalt (II) chloride respectively; he gelatin antistress layers of material A contained no co alt (II) compound.

Strips of the five materials were then stored for 36 hours in an atmosphere of 57 C. and 34% relative humidity and other strips of said materials were stored for 1 Week in said atmosphere.

The stored material strips as well as strips of the freshly prepared materials were exposed and developed for 8 minutes at C. in a developing bath having the same composition as that of Example 1.

After the treatment in a stop bath, rinsing and fixing of the material strips the following sensitometric results were attained.

From these results it appears that the cobalt (II) chelates of the invention have a markedly better anti fogging action than the known cobalt (II) compounds, without giving rise to an appreciable desensitization. Cobalt (II) chloride has also a good fog-inhibiting action but has a higher desensitizing effect.

EXAMPLE 4 Example 3 was repeated with the diiference, however, that the antistress layers of materials D and E comprised,

in lieu of thementioned'cobalt (II) salts, equivalent amounts per sq. m. of ethylene diamine tetraacetic acid sodium salt (EDTA Na-salt) and of an aqueous solution of cobalt (II) sulphate and EDTA-Na-salt respectively.

. cobalt (II) chelate from a solution of cobalt (II) sulfate and ethylene diamine tetraacetic acid sodium salt (mate rial E) has the same favorable fog-inhibiting effect as the addition as such of the cobalt (II) chelate of compound 1 disodium'salt (material B). The better fog-inhibiting eifect of the cobalt (II) chelates as compared with known cobalt (II) compounds is even the more surprising in view of the fog produced in materials C and D' where cobalt (II) sulfate and EDTA-Na-salt are used alone.

' Analogous tests as described in the above. Examples 1 to 4 were carried out with the cobalt (II) chelates of compounds 4, 5, 8, 9 and 13. The same favorable stabilizing and fog-inhibiting effects were obtained.

EXAMPLE 5 A gelatino silver bromoiodide emulsion as describedin Example 1 was. divided into 2 aliquot portions.

I Each of the two emulsion portions was coated on both sides of .a'subbed cellulose triacetate support, in such a way that on both sides an amount of silver halide equivalent to 8 g. per sq. m. of silver nitrate was present, and dried. The emulsion layers of the two materials A and B were then overcoated with a gelatin antistress layer, the antistress layers. of material B containing-0.07 g. per sq. m. of the manganese (II) chelate of compound 1 di-v ,sodium salt.

Strips of the two materials were stored for 36 hours in an-atmosphere of 57 C. and 34% relative humidity. The stored material strips as well as strips of the freshly prepared materials were exposed and developed for 8 minutes at 20 C.- in a developing bath as described in Example 1.

After the treatment in a stop bath, rinsing andfixing of the material strips the following sensitometric results were attained.

54 04.34% RH I Relative I Relative Gratlaspeed, Gradaspeed,

' Material Fog tion percent Fog tion percent A 0. 11 3. 11 0. l8 2. 91 115 B 10 3. 25

0.11 ao'z Analogous tests, as described in'the above Example 5,

. 1. Photographiclight-sensitive silver halide emulsion comprising in said emulsion at least one cobalt (II) or manganese (II) chelate of a (poly)amino-(poly)earboxylic acid in acid form or in the form of a water-soluble salt wherein said (poly)amino-(poly)carboxylic acid corresponds to the following general formula:

R2 R1 N L N RCOOII 2. Photographic light-sensitive silver halide emulsion according to claim 1, wherein said cobalt (II) or man ganese (II) chelate is present in an amount of from 0.1 g. to 20 g. per mole of silver halide.

3. Photographic light-sensitive silver halide emulsion according to claim 1, wherein said emulsion also comprises a stabilizer of the hydroxytriazolo-pyrimidine type.

4. Photographic light-sensitizer silver halide emulsion according to claim 1, wherein the emulsion is a gelatino silver halide emulsion.

5. Photographic light-sensitive silver halide material comprising in a gelatin anti-stress layer coated over a silver halide emulsion layer at least one cobalt (II) or manganese (II) chelate of a poly(amino)-(poly)carboxylic acid in acid form or in the form of a water-soluble salt wherein said (poly) amino-(poly)carboxylic acid corresponds to the following general formula:

RILN L -N R stands for lower alkylene including substituted lower alkylene, and

each of R and R (the same or different) stands for hydrogen, lower alkyl including substituted lower alkyl, aralkyl including substituted aralkyl or aryl including substituted aryl.

6. Photographic material according to claim 5, wherein said cobalt (II) or manganese (II) chelate is present in an amount of from 1 0 mg. to 1 g. per sq. m. of gelatin anti-stress layer.

7. A process of stabilizing photographic light-sensitive silver halide emulsions, which process comprises exposing to light and developing the light-sensitive silver halide emulsion containing at least one cobalt (II) or manganese (II) chelate of a (poly)amino-(poly)=carb0xylic acid in acid form or in the form of a water-soluble salt, said (poly)amino-(poly)carboxylic acid having the general formula:

R-oooH wherein:

References Cited UNITED STATES PATENTS 2,666,700 1/1954 Baldsiefen 96107 2,910,359 10/1959 Maifet 96-110X NORMAN G. TORCHIN, Primary Examiner J. D. WINKELMAN, Assistant Examiner 

